The present disclosure relates to pressurized gas release valves, and more particularly, to a solenoid-operated pressure-balanced poppet valve having no dynamic seals.
Poppet valves are commonly used in flow control applications where release of a gas from the valve must be controlled in both timing and quantity. As a simplistic example, a poppet valve has a channel that is closed off by a biased poppet, which is a disc-shaped plug on the end of a shaft. The poppet may be held closed against a seat by a spring, and may further be held closed by a pressure differential across sides of the poppet. A change in the pressure differential can either open or close the poppet depending on how it is configured.
In a balanced poppet valve, all forces acting on the poppet are substantially equal in the equilibrium (closed or open, hereinafter “balanced”) state, so that only a small force is needed to actuate the valve. Typically, the balanced state is closed, with a light gauge spring holding the poppet closed. A balanced poppet valve may be actuated by a solenoid, which magnetic force only has to overcome the biasing force of the spring to actuate the valve. The low force required allows for quick actuation.
Balanced poppet valves with a single poppet are employed in a wide range of applications, including industrial process controls and internal combustion engines. In high-pressure applications, balanced poppet valves having two coaxial poppets improve the valve functionality over a single poppet because the pressure on one plug balanced the pressure on the other. Such two-poppet valves were used as early as the mid-19th century in steam engines, and into the 20th century they were used with solenoid actuators for some metering applications. However, historically such valves have suffered from a widely-acknowledged leakage problem due to the design and materials used. In particular, relatively modern two-poppet pressure-balanced valves have metal seats, which are durable but do not create a reliable seal for the two metal poppets that must be seated simultaneously. Thus, application of modern two-poppet balanced valves is limited to uses where direct solenoid drive of the valve is needed but leakage is not critical.
Previous attempts to overcome the drawbacks of balanced poppet valves in high-pressure applications where leakage is critical have utilized one or more dynamic seals to address the leakage. A dynamic seal is created between two surfaces that are moving relative to each other. Such a seal generates a large amount of friction. In pressure-balanced poppet valve, the friction from the dynamic seal requires generation of additional force to overcome it when actuating the valve. In turn, a larger and heavier solenoid is needed to generate the additional force.
Thus, existing balanced poppet valve designs are unsuitable for ultra-high performance applications that require fast actuation, near-zero leakage, and low weight. An illustrative example addressed in the present disclosure is an ejection system for a crew compartment of an aeronautical craft. The ejection system must be designed to minimize the time between when the system is activated and when it propels the compartment away from the rest of the craft. As described further below, propulsion may include regulated release of a high-pressure gas. The valves of the regulator must be designed to open and close extremely fast in use, but also must seat precisely at each actuation and must not leak. The valves must contribute as little weight as possible to the ejection system, keeping down the overall weight of the crew compartment and the craft. The valves must also withstand the extreme conditions of the application, including extremely high fluid pressures (up to 10 kpsi or higher), extreme temperatures and temperature variation (from sub-zero to well above zero), material deformation due to pressure and thermal stresses, and vibrations and stresses due to high speeds of the craft. Finally, the valves must be compatible with the gases used in the system, such as gaseous Helium (GHe) and corrosive hypergolic propellants like nitrogen tetroxide (N2O4) and monomethylhydrazine (MMH). A balanced poppet valve capable of functioning in this application is needed.